Machine vision systems are used in numerous applications including, in particular, in electronics manufacture and assembly, such as inspection of electronic components, die alignment and inspection, package singulation inspection and lead inspection.
In one example, a video camera is placed at a fixed location with respect to one or more objects to be viewed. Knowing the location of the camera and the field of view of the camera optics, specific information can be obtained about the objects. The video information can be analyzed mathematically to obtain information that may be manipulated and stored.
In one example, integrated circuits are placed in a JEDEC tray for examination under a machine vision inspection system. It is of interest to discern the relative location of connection pads on the integrated circuit with respect to the edges of the integrated circuit packages. Thus, it is important to be able to discriminate the pads from the edges of the package.
In order to be able to discriminate the pads from the edges of the package, the reflected illumination off the pads should to be clearly distinguishable from the package edges and background. In many cases, the reflectance of the pads and edges are too similar to be able to clearly and automatically distinguish and differentiate the two. In other applications, the reflected light from the pads is so great as to cause bloom in the video camera and obscure the edges.
Where there is a sufficient difference in height between the background and objects, point illumination at an angle can help to make the object edges show up more clearly. However, often such height differences do not exist.
What is needed is a system and method that is able to reliably and clearly distinguish between objects in the field of view of the video camera.